Mansard Roof Extensions in Hillingdon

Which postcode districts around Hillingdon do we cover for mansard roof extension work?

Every Hillingdon postcode district we draw in, the stock that dominates it and the authority that validates a mansard roof extension there. Hillingdon fees below are the statutory England rates for 2026, not mansard roof extension estimates.

How does a mansard roof extension differ street by street across Hillingdon?

Roof pitch, wall build-up and plot depth change every few Hillingdon streets, and each one changes what a mansard roof extension can achieve at that address.

• West Drayton (UB7) — a mansard roof extension in West Drayton starts from 1930s semi-detached, post-war, and West Drayton reads as 1930s semi-detached. Mansards are rare on 1930s stock — the hipped roof form works against the geometry in UB7. Hillingdon Council assesses West Drayton mansard roof extensions against its own West Drayton character guidance, and the location plan we draw for West Drayton references West Drayton station.
• Ickenham (UB10) — a mansard roof extension in Ickenham starts from 1930s semi-detached, tudor fragments, and Ickenham reads as 1930s semi-detached, village conservation. Mansards are rare on 1930s stock — the hipped roof form works against the geometry in UB10. Hillingdon Council assesses Ickenham mansard roof extensions against its own Ickenham character guidance, and the location plan we draw for Ickenham references Ickenham Village.
• Harefield (UB9) — mansard roof extension work in Harefield means tudor and georgian fragments, 1930s semi-detached. Harefield is village conservation, rural fringe. Mansards read as original on Georgian terraces throughout UB9. Hillingdon Council decides the Harefield application, and Harefield Hospital anchors the Harefield location plan.
• Yiewsley (UB7) — mansard roof extension work in Yiewsley means 1930s semi-detached. Yiewsley is 1930s semi-detached. Mansards are rare on 1930s stock — the hipped roof form works against the geometry throughout UB7. Hillingdon Council decides the Yiewsley application, and Yiewsley High Street anchors the Yiewsley location plan.
• Eastcote (HA5) — 1930s semi-detached defines Eastcote, where 1930s semi-detached set what a mansard roof extension can do. Mansards are rare on 1930s stock — the hipped roof form works against the geometry across HA5. Any Eastcote mansard roof extension is validated by Hillingdon Council, with Eastcote Tube the usual Eastcote reference point on the site plan.
• Hillingdon (UB10) — 1930s semi-detached, post-war defines Hillingdon, where 1930s semi-detached set what a mansard roof extension can do. Mansards are rare on 1930s stock — the hipped roof form works against the geometry across UB10. Any Hillingdon mansard roof extension is validated by Hillingdon Council, with Hillingdon Tube the usual Hillingdon reference point on the site plan.
• Uxbridge (UB8) — a mansard roof extension in Uxbridge starts from georgian fragments, 1930s semi-detached, post-war flats, and Uxbridge reads as Georgian centre, 1930s residential. Mansards read as original on Georgian terraces in UB8. Hillingdon Council assesses Uxbridge mansard roof extensions against its own Uxbridge character guidance, and the location plan we draw for Uxbridge references Uxbridge High Street.

Does Hillingdon planning policy restrict a mansard roof extension?

How designation changes a Hillingdon mansard roof extension: Hillingdon Council maintains 29 conservation areas, including Uxbridge, Ruislip Village, Northwood. Inside any of them a Hillingdon mansard roof extension cannot rely on permitted development, and the route becomes a £548 householder application determined in 8 weeks rather than a £249 prior approval in 6 weeks. Ruislip Village sets the tone for Hillingdon casework.

Hillingdon permitted development status: there is no borough-wide direction from Hillingdon Council, so a mansard roof extension at a HA4 address is normally still permitted development. We certify that with a £274 Lawful Development Certificate rather than leaving a Hillingdon sale to argue it later.

What Hillingdon is built from: 1930s semi-detached dominates; Metropolitan Green Belt covers much of north Hillingdon; Victorian cottages in Uxbridge and Ruislip villages; post-war housing near Heathrow. Largest outer west London borough; significant Green Belt; Heathrow noise contours affect planning decisions in Harmondsworth and Sipson. That mix decides the mansard roof extension route in Hillingdon more than the postcode does, and it is what a Hillingdon Council case officer reads first. A householder application costs £548 paid to Hillingdon Council direct, with 8 weeks to a decision once validated.

Who decides a mansard roof extension on the edge of Hillingdon?

• Harrow — cross the Hillingdon boundary and Harrow Council takes the mansard roof extension instead, applying 29 conservation areas of its own around HA1. We re-price mansard roof extensions at the Hillingdon edge because Harrow policy and Hillingdon policy rarely align on mansard roof extension depth.
• Ealing — adjoining Hillingdon, with 30 conservation areas centred on W3. A mansard roof extension on the far side of the Hillingdon line is determined by Ealing Council, so the Hillingdon quote for mansard roof extensions is checked against Ealing guidance before it is issued.
• Hounslow — the Hounslow boundary runs against Hillingdon, so a mansard roof extension a street from Hillingdon is decided by Hounslow Council instead. Hounslow runs 30 conservation areas across W3 and its neighbours, which is why mansard roof extensions priced for Hillingdon are re-checked against Hounslow policy whenever the Hillingdon address sits on that edge.

Sources for this Hillingdon mansard roof extension page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.